Evidence for the presence of an endogenous cytosolic protein inhibitor of intestinal fucosyltransferase activities.
Soluble endogenous inhibitory activities for glycoprotein: alpha (1-2) and alpha (1-3) fucosyltransferases are demonstrated in rat small intestinal cytosol. These inhibitors are retained on DEAE-cellulose and are eluted as two fractions A and B. Fraction B is non dialyzable, heat stable and pronase-resistant and consists probably of poly-nucleotides. Fraction A is also non-dialyzable, but is thermolabile and pronase-sensitive, suggesting that it contains proteins. The inhibition of fucosyltransferase activity by fraction A is competitive for GDP-fucose and non-competitive for the glycoprotein substrate. Inhibition is not due to interfering enzymatic activities (glycosyl-nucleotide pyrophosphatases, glycosidases or proteases) and is reversible. This protein inhibitor, with a molecular weight of 60,000, is found only in the intestine and the pancreas and appears to be different from the previously reported inhibitors of brain glycolipid glycosyltransferases.
Martin
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A
Department of General and Medical Biochemistry, Inserm-CNRS U189, Lyon-Sud Medical School, Oullins, France.
Ruggiero-Lopez
D
D
Biol
M C
MC
Louisot
P
P
D000818:Animals; D002852:Chromatography, Ion Exchange; D003600:Cytosol / Q000201:enzymology; D004791:Enzyme Inhibitors / Q000302:isolation & purification*; D005647:Fucosyltransferases / Q000037:antagonists & inhibitors*; D006602:Hexosyltransferases / Q000037:antagonists & inhibitors*; D007422:Intestines / Q000201:enzymology*; D007700:Kinetics; D051381:Rats; D011919:Rats, Inbred Strains
D004791:Enzyme Inhibitors; D005647:Fucosyltransferases; D006602:Hexosyltransferases